We don’t yet know if or when Note 7s outside of Korea will get the battery-limiting update.

The over-the-air update will begin at 2 a.m. KST on September 20 for any recalled Note 7 handsets still in the wild; there’s no suggestion that the OTA will affect safe replacement units. We’ve reached out to Samsung for details on whether recalled Notes in other regions will get a similar OTA.

While limiting battery charge levels may reduce the likelihood of further fires or explosions in unsafe Note 7s, it’s unclear what the side effects of actually applying the OTA will be. Android 6.0 phones like the Note 7 must recompile (or “optimize”) installed apps after most software updates — a CPU-intensive process which produces a fair amount of heat. Introducing extra heat to a possibly defective battery could cause its own problems.

Meanwhile Bloomberg has news of a previously unpublished preliminary report to Korean regulators on the cause of the Note 7’s battery issues. The report to the Korea Agency for Technology and Standards (KATS) body draws some early conclusions, but says more time is needed to pinpoint exactly what’s going on.

Initial conclusions indicate an error in production that placed pressure on plates contained within battery cells. That in turn brought negative and positive poles into contact, triggering excessive heat. Samsung however stressed that it needed to carry out a more thorough analysis to determine “the exact cause” of battery damage.

Samsung has publicly stated that a “battery cell issue” was responsible for incidents of fires and explosions — of which 70 have now been reported in the U.S. alone — however this is the first we’re hearing on the specific fault. Bloomberg echoes earlier reports that Samsung SDI, the group’s energy and battery company, was responsible for making most of the affected cells.

Update:Reuters now reports that Chinese firm ATL will become the main battery supplier for the Note 7 from now on.

Samsung will soon launch an online tool to let Note 7 owners check if their handset is affected, based on their phone’s unique IMEI number. The firm’s advice remains that if your Note 7 is affected, you should switch it off and return it under the recall program.